Automatic method and device for aiding the piloting of an airplane

ABSTRACT

A method is described for aiding the piloting of an airplane by ensuring availability of an automatic pilot that is normally controlled as a function of speed information of the airplane when the speed information is lost. The method includes detecting a loss of the speed information of the airplane. In response to the detection of the loss of the speed information, the method includes determining flight data of the airplane being independent from the speed information of the airplane, determining control parameters from the flight data, and controlling the automatic pilot based on the control parameters and without the speed information of the airplane. The automatic pilot includes an automatic piloting system or a flight director.

TECHNICAL FIELD

The present invention relates to an automatic method and device for aiding the piloting of an airplane, in particular a transport airplane, for commanding at least an automatic pilot and optionally, a thrust regulation system for the airplane.

Within the scope of the present invention, an automatic pilot comprises:

-   -   either an automatic piloting system of the AP (“Automatic         Pilot”) type, automatically acting on the control surfaces         (drift, ailerons, etc.) of the airplane so as to ensure the         guidance thereof;     -   or a flight director of the FD (“Flight Display”) type,         automatically displaying information on a display of the cockpit         of the airplane, allowing to aid the manual piloting carried out         by a pilot of the airplane.

BACKGROUND

As known, the automatic pilot (AP automatic piloting system or FD flight director) of a transport airplane, either coupled or not to a thrust regulation system, uses speed information in order to maintain a selection of the pilot and/or the speed field to values acceptable for the airplane.

If, during piloting, such speed information is lost, that is if it becomes unavailable, erroneous, or unreliable, the automatic pilot (AP automatic piloting system, FD flight director) and/or the thrust regulation system automatically disengage and/or maintain the current state of the airplane, leaving to the crew the charge of managing the situation.

Such a situation could occur, for example should the Pilot probes generally used for measuring the speed of the airplane, become iced-up. Such a situation is however exceptional, as most airplanes are provided with systems allowing the effects of icing to be limited or cancelled.

A disengagement of the automatic piloting system, the flight director and/or the thrust regulation system induces an additional workload for the crew that should process the cause of the breakdown, in addition to the usual tasks, and this, in an unusual situation wherein the speed information is lost.

The speed information is a primary parameter used by the automatic piloting system or the flight director, for defining the flight area of the airplane (high and low limits) and the dynamics of the airplane. An automatic pilot (AP, FD) or a thrust regulation system that would not respect such speed limits would lead the airplane to be unstalled or in an overspeed situation able to lead to structural damages. For this reason, the automatic pilot and the thrust regulation system are provided with different usual means protecting the speed area.

Consequently, when the speed information is lost, it is not possible to ensure the basic function of the automatic pilot (AP, FD) and the thrust regulation system in their current concepts, nor the protective functions of the flight area.

It should be furthermore noticed that a current automatic piloting system, a flight director and a thrust regulation system contain a high number of different operating modes each corresponding to an objective the crew can select as a function of their intentions. Learning such different modes and the transitions thereof represents a significant part of the crews' training. Thus, introducing new operating modes of the automatic piloting system, of the flight director and/or of the thrust regulation system generally requires a new learning phase, even of repeated training phase, if this mode is only of use in exceptional cases that generally do not occur in a normal use of the airplane.

SUMMARY OF THE INVENTION

The present invention relates to an automatic method for aiding the piloting of an airplane, allowing to ensure the availability of at least one automatic pilot (able to be controlled as a function of a speed information), that is an AP automatic piloting system or a FD flight director having the aim to overcome the above mentioned drawbacks.

To this end, according to this invention, said method is remarkable in that, automatically:

-   -   said speed information is monitored so as to be able to detect a         loss thereof; and     -   should a loss of speed information be detected, the following         operations are carried out:         -   the usual values of flight data of the airplane are             determined, being independent from said speed information;         -   control parameters are determined from said usual values of             flight data; and         -   such control parameters are used for ensuring the             availability at least of said automatic pilot (automatic             piloting system or flight director).

Within the scope of this invention, it is considered that a speed information is lost, when:

-   -   it is not available, for example as a result of a breakdown of         the measurement means or the information transmission means; or     -   it is available, but is erroneous or is not reliable. Such speed         information is considered as not reliable, when it cannot be         consolidated (for example as a result of the availability of one         single source of information). It could be considered as         erroneous when it meets some unlikelihood criteria.

Thus, according to this invention, should the speed information be lost, when being used more particularly by the automatic pilot (AP automatic piloting system or FD flight director), control parameters are determined by means of flight data that are independent from such a speed information, and these control parameters are used for ensuring the availability at least of said automatic pilot. Consequently, in such a situation of loss of the speed information, the automatic pilot should not be disengaged, but can go on operating, while maintaining the maximum of margin with respect to the authorized speed area, as set forth herein below. Such maintenance of the engagement of the automatic pilot makes it possible to overcome the above mentioned drawbacks, more particularly with respect to the crews' workload.

In a preferred embodiment, said method is also implemented for ensuring the availability, additionally, of a (automatic) thrust regulation system of the airplane. In this preferred embodiment, should the speed information be lost, said control parameters are used for also ensuring the availability of said thrust regulation system.

The present invention could also be implemented with or without control of a thrust regulation system of the airplane.

Furthermore, advantageously, should a loss of the speed information be detected:

-   -   an alarm is emitted to the crew of the airplane for example, as         a synthetic piece of information; and/or     -   said speed information is still monitored, and should an end of         a loss of speed information be detected, that is when said         information is no longer lost, such a speed information is used         again as a parameter for controlling said automatic pilot (and         optionally said thrust regulation system).

Moreover:

-   -   in a first embodiment, said automatic pilot is an automatic         piloting system of the AP type;     -   in a second embodiment, said automatic pilot is a flight         director of the FD type; and     -   in a third embodiment, the method according to this invention         ensures the availability simultaneously of both an automatic         piloting system and of a flight director.

In a particular embodiment, an automatic pilot is used, operating each time according to one of a plurality of possible different vertical guidance modes. In such a case, advantageously, some of said possible vertical guidance modes are selected, being referred to as selected vertical guidance modes, and, should a loss of the speed information be detected, said automatic pilot is operated according to one of said selected vertical guidance modes.

Preferably, said selected vertical guidance modes comprise:

-   -   an altitude maintaining mode for said automatic pilot,         optionally associated with a speed maintaining mode for said         thrust regulation system;     -   a constant thrust climbing mode, associated with a thrust         maintaining mode; and     -   a constant thrust descending mode, associated with a thrust         maintaining mode.

Such three selected vertical guidance modes allow:

-   -   the crew to better understand the current operating mode. The         use is further simplified, as the usual interfaces, enabling to         select a reference altitude and to generate level changes         (climbing/descending) or level flying, remain unchanged;     -   to manage to the best all the flight situations, for which the         automatic pilot is used (maintaining the flying level, climbing         then capture/maintaining the flying level, descent then         capture/maintaining the flying level); and     -   to obtain a guidance of the airplane, at short and medium terms,         being consistent with the initial objectives of the crew, and         this, whatever the initial situation upon the loss of speed         information.

In a first embodiment, the attitude of the airplane is used as a control parameter of the automatic pilot, and the engine speed as a control parameter of the thrust regulation system. Advantageously, such values are selected so as to maintain the speed of the airplane in the center of the flight area (so as to maximize the margins with respect to the minimum and maximum limits).

Preferably, said attitude and engine speed values are selected identical to the values currently supplied to the crew, in the usual procedure that the crew is to apply in the case of speed information being lost when the automatic pilot is no longer available.

Moreover, in a second embodiment, the incidence of the airplane is used as a control parameter of the automatic pilot, and the engine speed as a control parameter of the thrust regulation system. Advantageously, such a value of incidence is selected at the centre of the incidence field, that could be displayed, usually, instead of the speed scale, in the case of a loss of the speed information.

In a particular alternative embodiment, said first and second embodiments are combined so as to cover complementary flight areas. To this end, advantageously:

-   -   when the airplane is in a smooth aerodynamic configuration, the         attitude of the airplane and the engine speed of the airplane         are used as control parameters; and     -   when the airplane is in a sustained aerodynamic configuration,         the incidence of the airplane and the engine speed are used as         control parameters.

Within the scope of this invention, an aerodynamic configuration of the airplane means the position of the slats and flaps of the aerofoils of the airplane. Moreover, in a so-called smooth aerodynamic configuration, the slats and flaps are not extended, whereas in so-called sustained aerodynamic configurations, the slats and flaps are approximately extended.

The present invention further relates to an automatic device for aiding the piloting of an airplane, said device being of the type comprising an automatic pilot and optionally a thrust regulation system that are able to be controlled as a function of a speed information.

According to this invention, said device is remarkable in that it further comprises:

-   -   means for monitoring said speed information so as to be able to         detect a loss thereof;     -   means for determining, in the case where a speed information is         lost, the usual values of flight data of the airplane, being         independent from said speed information; and     -   means for determining, from said usual values of flight data,         control parameters, such control parameters being used for         ensuring the availability at least of said automatic pilot (and         optionally of said thrust regulation system).

The present invention further relates to an aircraft, in particular a transport airplane, comprising such a device.

BRIEF DESCRIPTION OF THE DRAWINGS

The unique FIGURE of the appended drawing will better explain how this invention can be implemented. This unique FIGURE is the block diagram of a device according to this invention.

DETAILED DESCRIPTION

The device 1 according to this invention and schematically shown on the FIGURE is intended to provide an aid to the piloting of an airplane (not shown), in particular of a transport airplane, comprising an automatic pilot 2 and an (automatic) thrust regulation system 3 (A/THR).

Within the scope of the present invention, an automatic pilot corresponds:

-   -   either to an automatic piloting system, of the AP (“Automatic         Pilot”) type, automatically acting on control surfaces (drift,         ailerons, etc.) of the airplane so as to ensure the guidance         thereof;     -   or to a flight director of the FD type (“Flight Display”) type,         automatically displaying information on a display of the cockpit         of the airplane, allowing to aid the manual piloting carried out         by a pilot of the airplane.

Such an automatic pilot 2 and such a thrust regulation system 3 could be usually controlled during normal operation as a function of a speed information of the airplane (e.g., as a function of information corresponding to the actual airspeed of the airplane). This speed information is determined by a usual airplane speed detection device 4, for example an air data and reference inertial unit, including of the Air Data Reference Inertial Unit (“ADIRU”) type, and is transmitted via links 5 and 6 respectively to said automatic pilot 2 and to said system 3.

According to this invention, said device 1 further comprises:

-   -   a speed information validation device 7 being connected via a         link 8 to the airplane speed detection device 4 and monitoring         said speed information so as to be able to detect a loss of the         latter;     -   a flight data value determination device 9 for determining, in         the case where a speed information loss is detected, the usual         values of flight data of the airplane, to be described later on,         being independent from said speed information; and     -   a control parameters determination device 10 being connected via         links 11 and 12 respectively to the speed information validation         device 7 and the flight data value determination device 9 and         being formed so as to determine, from said usual values of         flight data received from the flight data value determination         device 9, control parameters.

Such control parameters are then transmitted via links 13 and 14 respectively to said automatic pilot 2 and to said thrust regulation system 3, in order to ensure the availability at least of said automatic pilot 2 (and optionally of said system 3), as described hereinbelow.

Within the scope of the present invention, it is considered that a speed information is lost, when:

-   -   the speed information is not available, for example as a result         of a breakdown of the measurement device (e.g., the airplane         speed detection device 4) or of the information transmission         device (e.g., links) being used; or even     -   the speed information is erroneous or not reliable. A speed         information is considered as not reliable, when it cannot be         consolidated (for instance when only a single source of         information works normally). In addition, a speed information is         considered as erroneous when it meets some unlikelihood         criteria.

In a particular embodiment, such detection takes into consideration, for example:

-   -   the detection of an abnormal drop of the speed value, for         instance a drop by 30 kts (knots) in less than one second;         and/or     -   a lack of validation of two of the three speed measurements,         generally carried out on the airplane.

Thus, in the case of a loss of the speed information being used, more specifically, by the automatic pilot 2 and the system 3, the device 1 according to this invention determines control parameters from flight data being independent from such a speed information, and it uses such control parameters for said automatic pilot 2 (and optionally said system 3). Consequently, in such a situation, the automatic pilot 2 and (optionally) the system 3 are not disengaged, but they can continue to operate, while maintaining the maximum of margin, with respect to the authorized speed area, as described hereinbelow. Such maintenance of the operation of the automatic pilot 2 and of the system 3 allows, more specifically, the workload of the crew not to be increased in such a situation of loss of the speed information.

Moreover, said device 1 further comprises:

-   -   an alarm device 15 being, for example, connected via a link 16         to the speed information validation device 7 and which, in the         case where a loss of the speed information is detected, emit an         alarm to the crew, for instance, in the form of a synthetic         information being displayed on a screen 17 of the cockpit; and     -   a monitoring continuation device 18 being, for instance,         integrated into the speed information validation device 7 and         continuing to monitor said speed information, upon the detection         of a loss of such a speed information.

Generally, the meteorological phenomena causing a loss of the speed information, such as icing for example, are not permanent. Such phenomena generally have a limited duration over time. Thus, although the operating mode of the automatic pilot 2 according to this invention, allowing an operation without any speed information, is able to be used until the end of the flight, it could be interesting not to maintain this operating mode and to turn back to a usual operating mode, when the speed information becomes valid again.

Consequently, in a particular embodiment, in the case of the detection by the monitoring continuation device 18 of an end of the loss of speed information, the device 1 again uses such a speed information, usually, for the automatic pilot 2 (and optionally for the thrust regulation system 3).

It should be noted that, in cases where the speed information is erroneous or not reliable as upon icing, for instance, the altitude information being derived from a pressure measurement remains available, as it is measured by a probe that is not submitted to the problem linked to icing. The measurement could be slightly erroneous, as it is no longer correctly compensated by Mach effects, but such an error remains small. In addition, if the altitude measurement derived from a pressure measurement is not available, it is possible to use a measurement obtained from a satellite positioning system of the GNSS type.

In a particular alternative, the desired flight point (reference speed) for the airplane is determined as a function of the altitude (Zmes) of the airplane so as to be sufficiently remote from the high and low limits of the flight area.

A usual automatic pilot 2 (automatic piloting system of the AP type or flight director of the FD type) generally has numerous vertical guidance modes, as set forth hereinbelow as a non exhaustive illustration. With each vertical guidance mode a mode of the thrust regulation system 3 is associated.

Vertical guidance mode of Mode of the thrust the automatic pilot 2 regulation system 3 ALT: Altitude maintenance SPEED: Speed maintenance ALT*: Altitude capture SPEED: Speed maintenance SRS: Initial climbing and THR: Maintenance of a nosing up thrust OP CLB: Constant thrust THR: Maintenance of a climbing thrust OP DES: Constant thrust THR: Maintenance of a descent thrust VS: Maintenance of a SPEED: Speed maintenance vertical speed FPA: Maintenance of a SPEED: Speed maintenance slope CLB: Climbing according THR: Maintenance of a to a profile thrust DES: Descent according to SPEED or THR according to a profile the profile G/S: Maintenance of a SPEED: Speed maintenance

 glide 

 axis G/S*: Capture of a SPEED: Speed maintenance

 glide 

 axis

In such a case, the device 1 selects some of said possible different vertical guidance modes, being referred to as selected vertical guidance modes and, in the case where the speed information is lost, it actuates said automatic pilot 2 according to one of said selected vertical guidance modes.

In a particular embodiment, the device 1 only uses the following selected vertical guidance modes: ALT/SPEED, OP CLB/THR and OP DES/THR.

Such three selected modes allow:

-   -   to facilitate understanding by the crew of the usual operating         mode. The use is further simplified, as the usual interfaces,         allowing to select a reference altitude and to generate level         changes (climbing/descending) or level flying, remain unchanged;     -   to manage to the best all the flight situations, for which the         automatic pilot 2 is used (maintaining the flying level,         climbing then capturing/maintaining the flying level, descent         then capture/maintenance of the flying level); and     -   to obtain a guidance of the airplane, at short and medium terms,         being consistent with the initial objectives of the crew, and         this, whatever the initial situation upon the loss of speed         information.

The transitions between the initial state of the automatic pilot 2 upon the detection of the loss of the speed information and the final mode could be determined as a function of the initial mode as follows (with VSt a vertical speed and FPAt the slope):

Resulting mode Initial vertical guidance (without speed mode (before detection) information) ALT, ALT* ALT SRS, OP CLB, CLB OP CLB OP DES OP DES (|VSt| < 500 pieds/min) ALT (|FPAt| < 1°) (|VSt| < 500 pieds/min) OP CLB (|FPAt| < 1°) (|VSt| < 500 pieds/min) OP DES (|FPAt| < 1°) G/S, G/S* ALT

Alternatively, advantageously, the transitions between the initial state of the automatic piloting system at the time of the detection of unavailable, erroneous or unreliable, speed information, and the final mode could be determined as a function of the vertical speed of the airplane as follows:

Initial vertical speed Resulting mode (at the time of the (without speed detection) information) |VS| < 500 ft/min ALT VS > 500 ft/min OP CLB |VS| < 500 ft/min OP DES

Thanks to the alarm device 15, the crew can be informed of the new operating mode of the automatic pilot 2 (or of the system 3), of its limitations and of possible changes of modes that have occurred. In a particular alternative, a synthetic information, for instance “AP Alternate” and/or “FD Alternate”, being displayed on the screen 17 could be sufficient for understanding the new operating mode of the automatic pilot 2 (AP automatic piloting system or FD flight director).

In a first embodiment, the device 1 uses the attitude of the airplane as a control parameter of the automatic pilot 2, and the engine speed as a control parameter of the thrust regulation system 3. Preferably, such values are selected so as to maintain the speed of the airplane in the centre of the flight area (so as to maximize the margins with respect to the minimum and maximum limits).

Moreover, preferably, said attitude and engine speed values are selected to be identical to the values currently supplied to the crew, in the usual procedure that the crew are to apply in the case of speed information being lost when the automatic pilot 2 is no longer available. In a first possibility of this first embodiment, a guidance objective is considered according to the ALT mode.

In the usual ALT mode, the automatic pilot 2 (AP automatic piloting system or FD flight director) maintains an altitude, generally the altitude selected on the control unit (FCU) of the automatic pilot 2. At the flight point determined by the altitude of the airplane (Vref, Zmes), knowing the aerodynamics of the airplane, it is possible to determine, usually, the attitude .theta.ref and the engine speed Nlref as a function of the bulk (m) and of the aerodynamic configuration (conf) allowing for a stabilized level flying:

Θref=f(conf, m, Zmes)

Nlref=f(conf, m, Zmes)

In the case of the speed information being lost, the automatic piloting system slaves such an attitude value θref and the thrust regulation system 3 applies said engine speed Nlref.

Moreover, the flight director notifies the crew, either of this attitude value Θref, or of the deviation between this attitude value Θref and the current attitude of the airplane.

As a result of modeling errors, the balance point resulting from such values being slaved is close to the level, but is able to slowly deviate, and to make its operation incomprehensible to the crew. Thus, the attitude used by the automatic pilot 2 (AP automatic piloting system or FD flight director) is, on the one hand, adjusted so as to maintain the level flying, and on the other hand, limited so as, more specifically, to avoid too high an angle of attack likely to lead to stalling. Such a correction is further filtered so as to only keep the long term component allowing deviations to be avoided.

Furthermore, the difference θadj between the attitude θu determined for maintaining the level flying and the reference attitude θref is introduced again as an adjustment on the reference engine speed Nlref. The exchange rate between a thrust variation and the engine speed being generally known in the system 3, it is easy to convert an attitude variation (similar to a slope variation) into a thrust variation and, thus into a engine speed variation.

In this embodiment, the reference values θref and Nlref are identical, for the same bulks and flight levels, to those indicated in tables made available to the crew in the case of speed being lost.

The value θadj corresponds to the adjustment allowing for compensating the difference between the model of the airplane and the aerodynamics of the airplane.

In a second possibility of the first above mentioned embodiment, a guidance objective is considered according to one of the OP CLE or OP DES modes.

In a climbing/descent mode (respectively OP CLB/OP DES) the system 3 is maintained to the minimum/maximum (respectively Idle/CLB).

As the thrust is rigid, the automatic pilot 2 (AP automatic piloting system or FD flight director) slaves an attitude (θrefCLB, θrefDES) being determined, usually, as a function of the bulk (m) and of the altitude of the airplane (Zmes) knowing the reference speed (Vref) and the aerodynamic configuration (conf):

θrefCLB=f(conf, m, Zmes)

θrefDES=f(conf, m, Zmes)

Preferably, such values are identical, for the same flight bulks and levels, to those indicated in usual tables, made available to the crew, in the case of speed being lost.

Furthermore, the value θadj corresponding to the adjustment allowing to compensate for the difference between the model of the airplane and the aerodynamics of the airplane, could be also memorized and used in the OP CLB and OP DES modes so as to compensate for the differences between the model of the airplane and the aerodynamics of the airplane.

In this first embodiment, when the system 3 is not engaged, the above described operating mode of the automatic pilot 2 (AP automatic piloting system or FD flight director) does not allow to maintain the airplane in an acceptable speed area if the effective engine speed is significantly different from the reference speed.

Thus, in this case, the attitude used by the automatic pilot 2 is adjusted so as to compensate for the difference between the current speed Nlact and the reference speed Nlref.

An alternative comprises determining the attitude θu used by the automatic pilot 2 (AP automatic piloting system or FD flight director) as a function of the bulk, the altitude and the current engine speed:

θu=f(conf, m, Zmes, Nlact).

In these implementations, the attitude values are determined so as to correspond to table values supplied in the usual procedures, when the current engine speed corresponds to values of those tables.

In these implementations, the crew could manually adjust the thrust, maintain the level flying, bring the airplane in a descent mode (reducing the throttle lever) or in a climbing mode (increasing the throttle lever).

Such an operating mode of the automatic pilot 2 (AP automatic piloting system or FD flight director) is thus acceptable for all the flight phases of the airplane.

Furthermore, in a second embodiment, said device 1 uses the angle of attack of the airplane as a control parameter of the automatic pilot 2, and the engine speed as a control parameter of the thrust regulation system 3. Preferably, such a value of angle of attack (reference angle of attack) is selected at the centre of the angle of attack field, which could be displayed, usually, instead of the speed scale, in the case of a loss of the speed information.

In such a case, the automatic piloting system carries out slaving on this reference angle of attack.

Moreover, the flight director displays a deviation between the angle of attack of the airplane and the reference angle of attack.

In a first possibility of this second embodiment, a guidance objective is considered according to the ALT mode.

Similarly to the first above mentioned embodiment, the automatic pilot 2 (AP automatic piloting system or FD flight director) and the thrust regulation system 3 could slave an altitude using the reference angle of attack (determined from the configuration) and an engine speed Nlref determined for maintaining the level flying at the reference angle of attack α:

Aref=f(conf)

Nlref=f(conf, m, Zmes)

Furthermore, the angle of attack used by the automatic pilot 2 (AP automatic piloting system or FD flight director) is adjusted so as to maintain the level flying, and it is limited so as, more specifically, to avoid too high an angle of attack likely to lead to stalling. Such a correction is further filtered so as to only keep the long term component allowing deviations to be avoided.

Moreover, the difference between the angle of attack au determined for maintaining the level flying and the reference angle of attack α is introduced again as an adjustment on the reference engine speed Nlref. The exchange rate between a thrust variation and the engine speed being generally known in the system 3, it is easy to convert an angle of attack variation (similar to a slope variation) into a thrust variation and, thus into a engine speed variation.

In a second possibility of the first above mentioned embodiment, a guidance objective is considered according to one of the OP CLB or OP DES modes.

In this case, the reference angle of attack α can also be used for climbing or descent, while adapting through the system 3 the engine speed to a minimum value (Idle) for the descent and to a maximum value (CLB) for the climbing. The automatic pilot 2 (AP automatic piloting system or FD flight director) enslaves the angle of attack as a function of the thrust.

Furthermore, when the system 3 is not engaged, the operating mode of the above described automatic pilot 2 allows the airplane to be maintained in an acceptable angle of attack area. The pilot could, through thrust adjustments, select the slope of the airplane (approximately maintaining the level flying, climbing, descent).

Furthermore, in a particular alternative embodiment, said first and second embodiments are combined so as to cover complementary flight areas. In such a case:

-   -   when the airplane is in a smooth aerodynamic configuration (with         unextended slats and flaps), the device 1 uses as control         parameters the attitude of the airplane and the engine speed;         and     -   when the airplane is in a sustained aerodynamic configuration         (slats and flaps are more or less extended), said device 1 uses         as control parameters the angle of attack of the airplane and         the engine speed. 

The invention claimed is:
 1. A method for aiding piloting of an airplane by ensuring availability of an automatic pilot that is normally controlled as a function of speed information of the airplane when the speed information is lost, the method comprising: detecting a loss of the speed information of the airplane; and in response to the detection of the loss of the speed information of the airplane: determining flight data of the airplane, the flight data being independent from the speed information of the airplane; determining a plurality of control parameters from the flight data; and controlling the automatic pilot based on the control parameters and without the speed information of the airplane, wherein the automatic pilot comprises an automatic piloting system or a flight director.
 2. The method according to claim 1, wherein the automatic pilot is an automatic piloting system.
 3. The method according to claim 1, wherein the automatic pilot is a flight director.
 4. The method according to claim 1, wherein the automatic pilot includes both an automatic piloting system and a flight director.
 5. The method according to claim 1, wherein the automatic pilot operates according to one of a plurality of possible different vertical guidance modes, and the method further comprises: prior to the detection of the loss of the speed information of the airplane, operating the automatic pilot according to any one of the possible different vertical guidance modes; and in response to the detection of the loss of the speed information of the airplane, operating the automatic pilot according to one of a selected subset of the possible different vertical guidance modes, the selected subset of the possible different vertical guidance mode being referred to as selected vertical guidance modes.
 6. The method according to claim 5, wherein the selected vertical guidance modes comprise: an altitude maintaining mode; a constant thrust climbing mode; and a constant thrust descending mode.
 7. The method according to claim 1, further comprising: in response to the detection of the loss of the speed information, emitting a warning to a crew of the airplane.
 8. The method according to claim 1, further comprising: continuing to monitor the speed information after the detection of the loss of the speed information; and in response to an end of the loss of the speed information being detected, controlling the automatic pilot based on the speed information.
 9. The method according to claim 1, further comprising: in response to the detection of the loss of the speed information, controlling a thrust regulation system of the airplane based on the control parameters and without the speed information of the airplane, thereby ensuring availability of the thrust regulation system when the speed information is lost.
 10. The method according to claim 9, wherein controlling the automatic pilot based on the control parameters comprises controlling the automatic pilot based on an attitude of the airplane, and wherein controlling the thrust regulation system based on the control parameters comprises controlling the thrust regulation system based on an engine speed of the airplane.
 11. The method according to claim 9, wherein controlling the automatic pilot based on the control parameters comprises controlling the automatic pilot based on an angle of attack of the airplane, and wherein controlling the thrust regulation system based on the control parameters comprises controlling the thrust regulation system based on an engine speed of the airplane.
 12. The method according to claim 9, further comprising: when the airplane is in a smooth aerodynamic configuration, using an attitude of the airplane and an engine speed of the airplane as the control parameters for the automatic pilot and the thrust regulation system, respectively; and when the airplane is in a sustained aerodynamic configuration, using an angle of attack of the airplane and the engine speed of the airplane as the control parameters for the automatic pilot and the thrust regulation system, respectively.
 13. A device for aiding piloting of an airplane comprising: an automatic pilot that is normally controlled as a function of speed information of the airplane; a speed information validating device that detects a loss of the speed information of the airplane; a flight data value determination device that determines, in response to a detection of the loss of the speed information of the airplane, flight data being independent from the speed information of the airplane; and a control parameters determination device that determines, from the flight data, a plurality of control parameters used to control the automatic pilot without the speed information of the airplane, thereby ensuring the availability of the automatic pilot when the speed information of the airplane is lost, wherein the automatic pilot comprises an automatic piloting system or a flight director.
 14. The device according to claim 13, wherein the automatic pilot is an automatic piloting system.
 15. The device according to claim 13, wherein the automatic pilot is a flight director.
 16. The device according to claim 13, wherein the automatic pilot includes both an automatic piloting system and a flight director.
 17. The method according to claim 1, further comprising: operating the automatic pilot in a primary mode prior to the detection of the loss of the speed information of the airplane; and operating the automatic pilot in a secondary mode in response to the detection of the loss of the speed information of the airplane, wherein the speed information of the airplane is determined by a reference inertial unit during the primary mode. 